This changes one of the rules to use .box-title instead of h3,

for consistency with other rules.
It also changes the subsection styles to match what we had in RBCommons.

Nothing but RBCommons seems to use this style currently, and I don't

know why the style differed from what we had there, but worth moving it

back.

Tested this with Review Board and RBCommons. Saw the right styles for

RBCommons, and didn't see any issues with Review Board.